Optical communications use modulated light beams to convey information through optical fibers, free space, or waveguides. A beam of light can be modulated either directly by modulating current to a light source, or externally by using an optical modulator to modulate a continuous-wave light beam produced by the light source. External modulation has advantages in that it can handle higher power and frequencies; however, the required components can be larger, more complex, and more expensive.